Conventional rotary valves, viz., either of a type wherein a rotor is cylindrical and solid and has pockets, or of a type wherein a rotor is provided with radial blades, have several disadvantages. In particular, in the sealing parts on the sliding surface between the outer periphery of the rotary member and the inner periphery of the casing, if the valve is to convey powder particles, the powder particles will bite into the sliding surface, the wear will gradually increase due to the mutual friction, and the sealing performance will decrease greatly.
Therefore, in order to eliminate such disadvantages, there has been suggested a valve of a structure wherein sealing members such as packings formed of soft material, such as rubber, or sealing members formed of a wear-resisting metal are removably fitted to the outer peripheral part of the casing, or wherein sealing members are always resiliently pressed radially outwardly or inwardly with springs.
However, in readjusting the sealing surface pressures of such sealing members, the rotary valve must be disassembled, each sealing member must be adjusted, and the readjustment will entail complex operations. Further, it is difficult: to vary the sealing surface pressure of the sealing member to any pressure without disassembling the valve; to set and maintain the clearance in the sliding part of the sealing member to be precise; and to keep the clearance and sliding surface pressure of the sliding part of the sealing member always proper in conformity with the operating conditions of the apparatus. In the valve of the type wherein the sealing members are resiliently pressed with springs, there are disadvantages in that an extraordinary frictional force will act on the sealing member, the wear of the sealing member will increase sooner, and the life will be decreased. Further, in the valve of the type wherein springs are used, the spring load will vary (weaken) with the wear of the sealing member, the sealing surface pressure will vary, it will be difficult to perfectly correct for the wear, and the operations of disassembling and adjusting the valve at the time of readjusting the sealing surface pressure become more troublesome and complicated.
The present invention solves the foregoing disadvantages and problems.